Increased load on the respiratory muscles in obstructive sleep apnea

We wished to quantify, in patients with obstructive sleep apnoea (OSA), the activity of the respiratory muscles in relation to upper airway occlusion and patency in sleep. We hypothesized that particular levels of neuromuscular activation are directly associated with upper airway patency. 21 patients with previously diagnosed OSA and 21 healthy control subjects underwent respiratory muscle testing and polysomnography. Neural respiratory drive, as measured by the electromyogram of the diaphragm (EMG_di) was elevated in the obese OSA patients, awake and supine (13.1(5.6)%max), compared to normal subjects (mean (SD) 8.1(2.3)%max, p < 0.01). During unobstructed breathing in sleep (stage N2) normal subjects had an EMG_di of 7.7(3.9) compared to 22.8(19.2)%max in the OSA group (p < 0.001). Prior to airway occlusion, EMG_{submandibular} and EMG_di dropped markedly, and then, following occlusion, increased progressively to their highest levels at airflow onset. Patients with OSA require specific and increased levels of neural respiratory drive to sustain ventilation in sleep.     

Surface tension of upper airway mucosal lining liquid in obstructive sleep apnea/hypopnea syndrome

STUDY OBJECTIVES: The obstructive sleep apnea hypopnea syndrome (OSAHS) is a disorder characterized by repetitive closure and reopening of the upper airway during sleep. Upper airway luminal patency is influenced by the surface tension (gamma) acting within the liquid layer lining the upper airway. The aim of the present study was to examine the gamma of upper airway mucosal lining liquid (UAL) in both healthy subjects and patients with OSAHS before and after sleep. DESIGN: Measurements were performed before (PM) and after (AM) an overnight polysomnographic study. SETTING: Sleep laboratory. PARTICIPANTS: We studied 11 healthy adults (5 men, 6 women) and 15 patients with OSAHS (14 men, 1 woman). INTERVENTIONS: None. MEASUREMENTS AND RESULTS: The gamma of UAL ("pull-off' force technique, pooled PM and AM samples) in patients with OSAHS was increased (59.9 [53.8, 58.8] mN/m; mean [95% confidence interval]) compared with healthy subjects (56.3 [57.7, 62.1] mN/m; linear mixed effects models; P =.05). In both groups there was no significant difference between PM (56.6 [53.7, 59.5] mN/m for healthy subjects, 60.1 [57.9, 62.3] mN/m for the patients with OSAHS) and AM (56.1 [51.8, 60.4] mN/m and 59.6 [57.4, 61.8] mN/m, respectively) samples for gamma of UAL and salivary flow rate (5 minutes unstimulated collection; PM =0.53 [0.22, 0.84] mL/minute for healthy subjects, 0.38 [0.22, 0.54] mL/minute for OSAHS; AM=0.39 [0.23, 0.55] mL/minute and 0.32 [0.2, 0.44] mL/minute). However, the occurrence of nasal breathing during sleep was associated with a fall in gamma of UAL overnight (r2 = 0.15, P < .05). CONCLUSION: Patients with OSAHS have normal salivary flow rate but an increased gamma of UAL. In both healthy subjects and OSAHS patients, nasal breathing during sleep was associated with an overnight fall in the gamma of UAL.     

Collapsible upper airway segment to study the obstructive sleep apnea/hypopnea syndrome in rats

Animal models have been used to study the pathophysiology of the obstructive sleep apnea/hypopnea syndrome (SAHS). Nevertheless, in none of the models described to date have the animals been subjected to the different patterns of upper airway obstructive events (apneas, hypopneas, and inspiratory flow limitation) characterizing SAHS. Our aim was to devise and test a computer-controlled collapsible upper airway segment applicable to rats and able to realistically mimic obstructive SAHS events. The collapsible segment (total volume <2 cm(3) and a dead space of approximately 0.25 cm(3)) consisted of a Starling resistor based on a latex membrane subjected to an external pressure applied by a computer-controlled pressure source. The collapsible segment was tested in eight anaesthetized and tracheostomized rats. The upper airway segment allowed us to induce obstructive apneas and hypopneas with flow and inspiratory effort waveforms similar to the ones observed in patients with SAHS. This collapsible upper airway segment may be a useful tool to implement a rat model of SAHS.     

Evaluation of the upper airway in patients with obstructive sleep apnea

Multiple methods have been used to study the structure and physiological behavior of the upper airway (UA) in patients with obstructive sleep apnea (OSA). Valuable information may be obtained from the physiologic measurement of pressure and resistance along the UA, as well as from imaging techniques that include: direct or fiberoptic visualization, cephalometric roentgenograms, fluoroscopy, acoustic reflection, computerized tomography, and magnetic resonance imaging. This review summarizes the information that each of these methods has contributed to our understanding of the UA. The results obtained with these different methodologies have generally been complementary with structural narrowing being identified in the majority of patients with OSA. This narrowing is usually focal and located in the velopharyngeal or retropalatal segment of the UA. This is also the predominant site of initial UA collapse. Although obesity with enlargement of soft tissue structures is considered the predominant mechanism leading to UA narrowing, abnormal craniofacial development on a genetic or developmental basis plays an important contributory role.     

双相气道正压无创机械通气时阻塞性睡眠呼吸暂停综合征患者上呼吸道影像分析

目的 应用多层螺旋CT对阻塞性睡眠呼吸暂停综合征(OSAS)患者不同通气状态下上呼吸道行放射学成像,分析在全身麻醉无自主呼吸条件下双相气道正压(BiPAP)无创机械通气是否能克服上呼吸道阻力达到有效的机械通气.方法 选择拟行咽腭成形术的OSAS患者10例,手术前常规实施麻醉诱导睡眠.分别对患者清醒状态下自主呼吸(清醒期)、睡眠诱导后意识消失(诱导期)、BiPAP无创机械通气后5 min(通气期)时头部正位和侧位作螺旋CT扫描,测量上呼吸道各软组织区[软腭后区(RP)、舌根后区(RG)、会厌区(EPG)]的最窄气道横截面左右径、前后径长度及相应横截面积,并监测扫描过程中的无创血压(NIBP)、脉搏血氧饱和度(SpO2)、心率(HR)、自主呼吸频率(RR).结果 头颈部正位扫描显示诱导期RP区和EPG区最窄气道横截面左右径、前后径线长度比清醒期明显缩短,各区横截面积明显缩小[RP区:0.00(0.00,0.60)mm2比38.34(10.57,72.76)mm2,RG区:145.16(0.00,183.72)mm2比177.79(111.05,216.27)mm2,EPG区:39.02(7.55,86.36)mm2比154.69(124.74,322.00)mm2,均P＜0.05].通气期各横截面径线和面积较清醒期仍明显缩小(均P＜0.05),但与诱导期差异无统计学意义(均P＞0.05).头部侧位诱导期除RG区左右径外,各区最窄气道横截面左右径、前后径线长度均短于清醒期,横截面积亦缩小[RP区:0.00(0.00,18.74)mm2比61.46(36.77,141.46)mm2,RG区:69.75(35.74,214.83)mm2比287.68(197.01,393.18)mm2,EPG区:17.28(4.37,65.45)mm2比293.76(254.63,374.83)mm2,均P＜0.05].BiPAP通气时各区横截面径线与清醒期比较尚明显缩短,横截面积虽缩小却较诱导期明显回升(均P＜0.05).各期正、侧位NIBP、HR无明显变化,诱导期RR明显受抑制,SpO2降低(均P＜0.05),通气期RR、SpO2与诱导期比较虽有所改善,但差异无统计学意义(均P＞0.05),仍未回复到清醒期水平(均P＜0.05).结论 OSAS患者睡眠诱导后上呼吸道通畅度明显下降,即使将头部侧位后仍未能改善上呼吸道的通畅度,无自主呼吸的状态下应用BiPAP无创机械通气不能克服上呼吸道阻力达到有效通气,需特殊处理保证安全.     

双相气道正压无创机械通气时阻塞性睡眠呼吸暂停综合征患者上呼吸道影像分析

Objective Multislice spiral CT scanning was used for radiological imaging of upper airway under various ventilation in obstructive sleep apnea syndrome (OSAS) patients in order to study whether bi-level positive airway pressure (BiPAP) noninvasive mechanical vetilation can overcome upper airway resistance and provide effective ventilation under general anesthesia and non-spontenuous breathing.Methods Ten OSAS patients scheduled for uvulopalatopharyngoplasty were enrolled in the study. General anesthesia inducing sleep was routinely performed before operation. Computer tomography of cephal-neck in orthophofic and lateral position was performed under spontaneous respiration (lucid interval) , nonconsciousness after sleep induction (induction period), and noninvasively ventilation with BiPAP for 5 min (ventilation period). Narrowest transverse and anteroposterior diameters of transverse section, and correlative cross section areas over each soft tissue region of upper respiratory tract [retropalatal (RP) ,retroglossal (RG) and epiglottal (EPG) region] were tested. Noninvasive blood pressure (NIBP), oxygen saturation by pulse oximeter (SpO2) , heart rate (HR) and spontaneous respiratory rate (RR) during scanning were monitored. Results In orthophoric position, transverse diameter and anteroposterior diameter of RP and EPG regions shortened during anesthesia induction. Cross section area of all regions decreased during anesthesia induction [RP region: 0.00(0.00, 0.60) mm2 vs 38.34(10.57, 72.76) mm2, RG region:145.16(0.00, 183.72) mm2 vs 177.79(111.05, 216.27) mm2, EPG region: 39.02(7.55, 86.36) mm2 vs 154.69 (124.74, 322.00) mm2, all P＜0.05]. The diameters shortened and area decreased as well under BiPAP ventilation when comparing with those in spontaneous respiration (all P＞0.05) , however, no statistical significance was found when comparing with those in induction period (all P＞0.05). In lateral position, diameters and areas under BiPAP ventilation were smaller than those during spontaneous respiration except for transverse diameter of RG region[areas, BP region: 0.00(0.00, 18.74) mm2 vs 61.46(36.77, 141.46) mm2, RG region: 69.75 (35.74, 214.83) mm2 vs 287.68 (197.01, 393.18) mm2, EPG region: 17.28 (4.37, 65.45) mm2 vs 293.76(254.63, 374.83) mm2, all P＜0.05] The transverse diameter,anteroposterior diameter and transverse section area during BiPAP ventilation decreased also when comparing with those in spontaneous respiration, however, transverse section area increased significantly during induction period (all P＞0.05). Neither NIBP nor HR changed both in orthophoric and lateral position. RR at induction period was obviously inhibited and SpO2 decreased (all P＜0.05). Though RR and SpO2 during ventilation period improved as compared to induction period, however no statistical significance was observed (all P＞0.05), none of them returned to normal range (all P＜0.05). Conclusion The ventilation of upper airway is not smooth after sleep induction in OSAS patients, though their heads are in lateral postion. By BiPAP noninvasive ventilation, effective ventilation still can not be achieved since airway resistance is not relieved, so special handling is advised to ensure safety.     

Genetic determinants of upper airway structures that predispose to obstructive sleep apnea

Genetic factors are thought to play an important role in human development. Recent data indicate that obstructive sleep apnea may have a genetic basis. Sleep apnea is a very common disorder with significant cardiovascular and neurophysiologic morbidity. The pathogenesis of sleep apnea is related to a reduction in the size of the upper airway. The reduction in airway size is secondary to increased adipose tissue (enlargement of the parapharyngeal fat pads), alterations in craniofacial structure (reduction in mandibular size) and enlargement of the surrounding soft tissue structures (tongue, lateral pharyngeal walls). Genetic factors are one of the factors that have been proposed to mediate the size of each of these anatomic risk factors for sleep apnea. Recent evidence is accumulating about the genetic loci for these structural risk factors that predispose to the development of obstructive sleep apnea.     

Brief airway occlusion produces prolonged reflex inhibition of inspiratory muscles in obstructive sleep apnea

STUDY OBJECTIVES: The human inspiratory muscles respond to a brief occlusion of the upper airway during inspiration with a profound short-latency reflex inhibition. This inhibition contrasts with the excitatory stretch reflex of limb muscles and may protect the airway from aspiration. It was postulated that this reflex would be altered in subjects with obstructive sleep apnea (OSA) who have repetitive upper airway occlusion. DESIGN: Subjects underwent overnight polysomnography, as well as muscle reflex studies. For the reflex studies (performed during wakefulness), occlusions lasting 250 milliseconds were delivered during inspiration. Surface electromyogram was recorded over the scalenes, parasternal intercostals, and chest wall (overlying diaphragm). SETTING: Research and sleep laboratories. PARTICIPANTS: Nineteen subjects with untreated OSA (9 moderate and 10 severe) and 9 healthy control subjects. MEASUREMENTS AND RESULTS: In the subjects with severe OSA, the duration of the inhibition was prolonged by at least 25% compared with control subjects. The peak of the inhibitory response for scalenes occurred significantly later for subjects with severe OSA than for control subjects (by 76 +/- 5 ms vs 60 +/- 3 ms [mean +/- SEM], respectively). Onset latencies of the later excitatory response were delayed for scalenes, parasternal intercostals, and chest wall recordings (eg, scalenes: 105 +/- 9 ms for subjects with severe OSA vs 83 +/- 5 ms for control subjects). CONCLUSIONS: The latency of peak inhibition and duration of inhibition were positively correlated with the respiratory disturbance index for all muscle groups. These changes may reflect adaptation in central respiratory paths due to repetitive loading during sleep.     

Morphologic analyses of mandible and upper airway soft tissue by MRI of patients with obstructive sleep apnea hypopnea syndrome

STUDY OBJECTIVES: To evaluate the morphological features of the mandible and the volume of the upper airway soft tissues in determining the anatomical risk factors for the upper airway in Japanese male patients with obstructive sleep apnea hypopnea syndrome (OSAHS). METHODS: Five morphological parameters of the mandible at the mandibular base plane and three volumetric parameters of the upper airway soft tissue were analyzed using three-dimensional (3D) magnetic resonance imaging software in 31 OSAHS and 20 controls. RESULTS: There were no significant differences between the two groups in mandibular internal width (the distance between the internal right and left gonia [IRG and ILG]) and mandibular bony thickness. However, the patients with OSAHS had a significantly wider mandibular divergence (the angle between the spina mentalis (SM)- IRG line and SM- ILG line), a smaller mandibular internal length (the perpendicular distance from SM to the RG- LG line), and a smaller area than the normal subjects at the mandibular base plane. There were no significant differences in these morphological parameters for the mandible between obese and nonobese OSAHS patients. The volumes of the tongue, soft palate, and lateral pharyngeal walls were not significantly different between the OSAHS and the control groups. CONCLUSIONS: Japanese male OSAHS patients had specific anatomical features in the bottom part of the mandible; however, obesity seemed to be a less significant risk factor. Investigators and clinicians must realize that ethnicity may modify the effects of obesity and abnormal craniofacial anatomy as risk factors for the pathogenesis of OSAHS.     

Magnetic resonance imaging of the upper airway in patients with quadriplegia and obstructive sleep apnea

The aim of this study was to investigate upper airway anatomy in quadriplegics with obstructive sleep apnea. Fifty subjects were recruited from three hospitals in Australia: people with quadriplegia due to spinal cord injury and obstructive sleep apnea (n = 11), able‐bodied people with obstructive sleep apnea (n = 18), and healthy, able‐bodied controls (n = 19). All underwent 3‐Tesla magnetic resonance imaging of their upper airway. A subgroup (n = 34) received a topical vasoconstrictor, phenylephrine and post‐phenylephrine magnetic resonance imaging. Mixed‐model analysis indicated no significant differences in total airway lumen volume between the three groups (P = 0.086). Spinal cord injury–obstructive sleep apnea subjects had a significantly larger volume of soft palate (P = 0.020) and retroglossal lateral pharyngeal walls (P = 0.043) than able‐bodied controls. Able‐bodied–obstructive sleep apnea subjects had a smaller mandible volume than spinal cord injury–obstructive sleep apnea subjects and able‐bodied control subjects (P = 0.036). No differences were seen in airway length between groups when controlling for height (P = 0.055). There was a marginal increase in velopharyngeal volume across groups post‐phenylephrine (P = 0.050), and post hoc testing indicated the difference was confined to the able‐bodied–obstructive sleep apnea group (P < 0.001). No other upper airway structures showed significant changes with phenylephrine administration. In conclusion, people with obstructive sleep apnea and quadriplegia do not have a structurally smaller airway than able‐bodied subjects. They did, however, have greater volumes of soft palate and lateral pharyngeal walls, possibly due to greater neck fat deposition. The acute response to upper airway topical vasoconstriction was not enhanced in those with obstructive sleep apnea and quadriplegia. Changes in upper airway anatomy likely contribute to the high incidence in obstructive sleep apnea in quadriplegic subjects.     

Practice parameters for the surgical modifications of the upper airway for obstructive sleep apnea in adults

Background:

Practice parameters for the treatment of obstructive sleep apnea syndrome (OSAS) in adults by surgical modification of the upper airway were first published in 1996 by the American Academy of Sleep Medicine (formerly ASDA). The following practice parameters update the previous practice parameters. These recommendations were reviewed and approved by the Board of Directors of the American Academy of Sleep Medicine.

Methods:

A systematic review of the literature was performed, and the GRADE system was used to assess the quality of evidence. The findings from this evaluation are provided in the accompanying review paper, and the subsequent recommendations have been developed from this review. The following procedures have been included: tracheostomy, maxillo-mandibular advancement (MMA), laser assisted uvulopalatoplasty (LAUP), uvulopalatopharyngoplasty (UPPP),radiofrequency ablation (RFA), and palatal implants.

Recommendations:

The presence and severity of obstructive sleep apnea must be determined before initiating surgical therapy (Standard). The patient should be advised about potential surgical success rates and complications, the availability of alternative treatment options such as nasal positive airway pressure and oral appliances, and the levels of effectiveness and success rates of these alternative treatments (Standard). The desired outcomes of treatment include resolution of the clinical signs and symptoms of obstructive sleep apnea and the normalization of sleep quality, the apnea-hypopnea index, and oxyhemoglobin saturation levels (Standard). Tracheostomy has been shown to be an effective single intervention to treat obstructive sleep apnea. This operation should be considered only when other options do not exist, have failed, are refused, or when this operation is deemed necessary by clinical urgency (Option). MMA is indicated for surgical treatment of severe OSA in patients who cannot tolerate or who are unwilling to adhere to positive airway pressure therapy, or in whom oral appliances, which are more often appropriate in mild and moderate OSA patients, have been considered and found ineffective or undesirable (Option). UPPP as a sole procedure, with or without tonsillectomy, does not reliably normalize the AHI when treating moderate to severe obstructive sleep apnea syndrome. Therefore, patients with severe OSA should initially be offered positive airway pressure therapy, while those with moderate OSA should initially be offered either PAP therapy or oral appliances (Option). Use of multi-level or stepwise surgery (MLS), as a combined procedure or as stepwise multiple operations, is acceptable in patients with narrowing of multiple sites in the upper airway, particularly if they have failed UPPP as a sole treatment (Option). LAUP is not routinely recommended as a treatment for obstructive sleep apnea syndrome (Standard). RFA can be considered as a treatment in patients with mild to moderate obstructive sleep apnea who cannot tolerate or who are unwilling to adhere to positive airway pressure therapy, or in whom oral appliances have been considered and found ineffective or undesirable (Option). Palatal implants may be effective in some patients with mild obstructive sleep apnea who cannot tolerate or who are unwilling to adhere to positive airway pressure therapy, or in whom oral appliances have been considered and found ineffective or undesirable (Option). Postoperatively, after an appropriate period of healing, patients should undergo follow-up evaluation including an objective measure of the presence and severity of sleep-disordered breathing and oxygen saturation, as well as clinical assessment for residual symptoms. Additionally, patients should be followed over time to detect the recurrence of disease (Standard).

Conclusions:

While there has been significant progress made in surgical techniques for the treatment of OSA, there is a lack of rigorous data evaluating surgical modifications of the upper airway. Systematic and methodical investigations are needed to improve the quality of evidence, assess additional outcome measures, determine which populations are most likely to benefit from a particular procedure or procedures, and optimize perioperative care.

Citation:

Aurora RN; Casey KR; Kristo D; Auerbach S; Bista SR; Chowdhuri S; Karippot A; Lamm C; Ramar K; Zak R; Morgenthaler TI. Practice parameters for the surgical modifications of the upper airway for obstructive sleep apnea in adults. SLEEP 2010;33(10):1408-1413.     

Influence of negative airway pressure on upper airway dynamic and impact on night-time apnea worsening

Background

Negative airway pressure loading such as seen during obstructive apnea/hypopnea may influence upper airway (UA) mechanical properties. We measured the effects of such loading on UA mechanical properties during wakefulness and assessed the potential link with night-time apnea worsening.

Methods

Twitch stimulations of the phrenic nerve were applied before and after a step-by-step increase in UA suction flow in 10 sleep apnea and 10 control males.

Results

Inspiratory closing pressure was lower in control than in apneic subjects. No consistent changes were observed in UA mechanical properties before and after the trial. In apneic patients, changes in the apnea index from the beginning to the end of the night correlated with changes in inspiratory closing pressure following suction flow.

Conclusion

(1) Apnea phenotype does not influence the impact of negative airway pressure on UA dynamic properties during wakefulness and (2) worsening of sleep apnea frequency during the night may relate to the exposure to recurrent UA negative pressure.     

Palatopharyngoplasty and obstructive sleep apnea syndrome

Thirty-five patients diagnosed with obstructive sleep apnea syndrome (OSAS) underwent palatopharyngoplasty (PPP) after an objective evaluation. They were all monitored polygraphically after surgery. The group's postsurgical results were positive, with significant improvement in the apnea-hypopnea index (A + H index) and oxygen desaturation. However, patients with hypopharyngeal or mandibular problems or massive obesity had poor postsurgical results. As no subject has been followed for longer than two years, the long-term prognosis for this surgical approach is unknown.     

阻塞性睡眠呼吸暂停低通气综合征的MRI研究

目的：探讨磁共振成像（MRI）对确定阻塞性睡眠呼吸暂停低通气综合征（OSAHS）病人阻塞部位的作用。方法：通过对35例OSAHS男性患者行多导睡眠仪、MRI及纤维喉镜检查配合Muller’s运动检查（FEMM）、同时对30例男性健康人的上呼吸道进行MRI检查，将两者检查结果进行比较，判定OSAHS患者上呼吸道狭窄的部位及狭窄程度，客观评价MRI对检查OSAHS患者的应用价值。结果：OSAHS患者的上呼吸道截面积明显小于健康人，轻度OSAHS患者多存在腭咽平面狭窄；中重度组OSAHA患者大部分所有平面都存在狭窄，但中度组以腭咽狭窄较明显，而重度组所有平面均存在较明显的狭窄，这种狭窄主要是由于口咽部周围软组织增生及软腭过长、肥厚及舌根宽大、肥厚所致。结论：MRI检查可判定OSAHS患者上呼吸道狭窄的部位及狭窄程度，有助于治疗方案的选择，对预估手术疗效具有重要的意义。     

Effect of upper airway surgery on heart rate variability in patients with obstructive sleep apnoea syndrome

To determine whether surgery influences cardiovascular autonomic modulation in obstructive sleep apnoea syndrome (OSAS), the present study was performed to evaluate the effect of upper airway (UA) surgery on heart rate variability (HRV) using frequency domain analysis for patient groups who have had either successful or unsuccessful surgery. We compared body mass index (BMI), polysomnographic [apnoea index (AI), apnoea-hypopnoea index (AHI), minimum SaO(2)] and HRV [very low frequency (VLF) power, low frequency (LF) power, high frequency (HF) power, HF/LF ratio, LFnu = LF/(LF + HF), HFnu = HF/(LF + HF)] parameters between the unsuccessful (n = 14) and successful (n = 22) surgical groups before and after UA surgery. Significant changes were observed for the successful patient group with respect to mean AI (from 29.1 ± 21.3 to 2.0 ± 3.2 events h(-1), P < 0.001), AHI (from 38.6 ± 20.0 to 5.6 ± 5.1 events h(-1), P < 0.001), minimum SaO(2) (from 73.3 ± 12.7 to 86.3 ± 6.5%, P < 0.001), VLF power (from 25599 ± 12906 to 20014 ± 9839 ms(2), P = 0.013), LF power (from 17293 ± 7278 to 14155 ± 4980 ms(2), P = 0.016), LFnu (from 0.700 ± 0.104 to 0.646 ± 0.128, P = 0.031) and HFnu (from 0.300 ± 0.104 to 0.354 ± 0.128, P = 0.031); however, mean BMI, HF power and LF/HF ratio did not change significantly after UA surgery. No significant changes were observed in the unsuccessful surgical group. Successful UA surgery may improve cardiac sympathetic and parasympathetic modulation in patients with OSAS.